1. Field of the Invention
The present invention relates to a drain valve used primarily for freeze protection on underground irrigation systems to prevent freeze damage to irrigation components such as pipe, sprinkler heads, valves and other assemblies.
2. Brief Description of the Prior Art
An underground irrigation system includes a main water line and a plurality of lateral lines. Each lateral line is connected through a water zone valve to the main line and feeds one or more sprinkler heads. Typically the main line is formed of PVC pipe and has a larger diameter and operates at a higher pressure than the lateral lines which may be formed of polyethylene tubing. In other systems, the main line and/or the lateral lines can be formed of polyethylene tubing, PVC pipe, copper pipe, galvanized pipe, etc.
In those regions where the ground freezes, it is necessary to drain the main line and the lateral lines at the beginning of the winter season to protect the water zone valves, sprinkler heads and pipes from freeze damage. The old way is to use air pressure to blow the water out of the system, an operation that is relatively expensive and requires specialized equipment. The newer way is to provide a drain valve in the lines. Freeze drain systems can include special tees, elbows, water zone valve protectors, etc., each of which (sometimes color coded for the "D.I.Y." customer) is outfitted with a drain valve, a representative line of which the installer, retailer or distributor must inventory. Other systems use a standard male pipe threaded drain in combination with tees, elbows, etc.
The water zone valves, sprinkler heads and drain valves in an underground irrigation system are often installed after the main line and lateral lines have been laid in a trench dug with a trencher or driven into the ground with a vibratory plow, etc. To install a currently available freeze drain valve mid-line in polyethylene tubing, a hole must be dug to expose the tubing, the line cut, ends trimmed and an inverted tee with the drain valve inserted and a pair of clamps installed over the ends of the tee to maintain a seal between the tee and the water line. The cost of installing a drain valve thus includes the labor cost of digging the hole, cutting and trimming the tubing and installing the tee and clamps, while the materials cost includes the tee with the drain valve, materials to treat the ends of the tubing and the pair of clamps.
From the installer's, retailer's and distributor's standpoint to minimize inventory, it would be desirable if there was a universal drain valve that could be used at various locations in the main or lateral lines to protect the water zone valves, sprinkler heads, lines, etc. from freeze damage. From the installer's standpoint, it would also be desirable to minimize the amount of digging, to avoid cutting and trimming the tubing and to eliminate the clamps, reducing the cost of installing a drain valve while also reducing the chance that the installer will cut corners by failing to install a drain where one is called for in the plan because of the amount of labor involved in installing a typical freeze drain.